KEITH FLETT discusses the history of counting protesters and questions its validity

THE LABOUR leadership contest between Jeremy Corbyn and Owen Smith has sparked renewed interest in the size of crowds and demonstrations. Of course if a meeting in a seated hall, the numbers attending can be accurately assessed. But most of the rallies held by the Labour leadership contestants have been held outdoors where judging numbers is much harder. The Guardian has published a piece suggesting that there is a sociological formula for working out the size of crowds.

Unfortunately crowds are comprised not of statistics but of real people who come and go and do all manner of things to frustrate an understanding of the numbers.

It is often taken that the police underplay numbers on protests — which has occasionally caused the left to slightly overplay them in response — unless, that is, the boys and girls in blue are seeking to justify a particularly high overtime bill, in which case they might exaggerate how many are there.

That said the police did have an official way of estimating numbers, which they used during the Stop the War demonstration in London on February 15 2003. This involved counting the number of people passing a certain point for a set amount of time and then extrapolating the size of the protest from that.

Government cuts in expenditure on the police seem to have ended the practice however.

It was one way of judging numbers but a moment’s thought suggests issues with it.

How is it known if the count is taken when the demonstration is at peak for example? How is account taken for the fact that people join and leave demonstrations throughout their duration? The argument about the size of demonstrations goes right the way back to the start of the modern movement.

On Monday April 10 1848 the Chartists gathered on Kennington Common to protest for the vote.

It was the first protest ever to be photographed and the photo still survives.

The problem is, what does the photograph show in terms of size?

We know that it was taken from outside the Common and it is thought that the picture was snapped well before the numbers at the protest peaked. Making the estimations even more tricky is the fact that in those pre-megaphone days there would have been several platforms with different speakers dotted around so that everyone in the Common to hear.

The press the following day played down numbers at the demonstration with the sole exception of the Chartist Northern Star, which had the largest circulation at that time.

Subsequent analysis of how many demonstrators could have been in Kennington Common on that day suggests 100,000 people — a large number even by today’s standards which would have been huge in 1848.

So photographs are one way of working out the size of a demonstration but only for a particular moment.

There is another slightly easier method purely involving maths. If, for example, Trafalgar Square is filled with a protesters, a rough estimation can easily be made by dividing the surface area of the square by the average space a person takes up. Hyde Park, however, would be much more complicated because, while it is a fixed space, the density of protesters could fluctuate much more rapidly as there’s more space to move.

Recent decades have seen some very large demonstrations, primarily in central London because there are so many people already in the area who can attend with little travel needed.

The CND and Stop the War campaigns have held huge protests as has the TUC. Perhaps another criterion we might think about though is not just size but impact. Jeremy Corbyn has held very large open air rallies in 2015 and again this year. Owen Smith less so.

When rallies such as those held by Corbyn make such an impact on a locality it frankly doesn’t matter so much what the BBC or the press think.